Before the law was in effect, background checks were only necessary for retail gun sales.

The bill for the universal background checks was sponsored by state Sen. Morgan Carroll[5], D-Aurora, and state Rep. Rhonda Fields[6], D-Aurora.

The measure was one of five bills passed by the Democratic-controlled legislature and signed into law by Gov. John Hickenlooper, despite stiff opposition from Republican lawmakers and Second Amendment[7] activists.